The present invention is especially adapted for use as a protective ground connection in a welding circuit and particularly direct current welding equipment where low impedence current paths can exist through mechanical components of the machinery. Particularly in automated welding equipment, it is difficult to maintain continuous integrity of electrical insulation between the welding current carrying circuit and the relatively complex mechanical parts of the apparatus under normal working conditions. Dust, metal chips, moisture, high temperatures and vibration all present the possibility of electric failures which can create electrical shock hazards to the machine operator. High to low transformer failures can apply the high primary transformer voltage directly to the secondary circuit. Even when the workpieces are grounded, the ground is only operative during welding periods and is not secure enough to protect personnel against transformer high to low failure. Where a secure ground is placed on the power supply for safety purposes, a parallel current path in the mechanical components is created which can jeopardize bearings and other movably engaged surfaces.
The present invention is especially directed toward the provision of a normally non-conductive connector which in response to a voltage fault in a monitored circuit will immediately establish a direct ground connection to the circuit.